Coolant fan wiring diagram showing the relay's connections to both switched and unswitched 12 volt sources

 

Hot at all times is primary power to the fan motor (switched via the relay contact). The switched is for the coil side of the relay (what make the contact close).

 

This is a factory schematic, right? So the low current side of the relay goes to the Choke/Heater fuse?
I was thinking of wiring my after market relay that way....

 

Yes that's a perfectly valid place to pick up "hot in run" from, if your car has that circuit. Since it's just the relay coil, and not the fan motor itself, the current it draws is very low; a small fraction of an amp. The wiring in that part of the circuit can be small; #18 or whatever. Other suitable places are the fuel pump relay circuit and the pink/black wire circuit.

The "hot at all times" wire must be LARGE. Like, #12 absolute bare minimum, #10 preferably. It should connect as electrically close to the + batt terminal as possible, the best spot being the + batt cable end at the big post on the starter. The fusible link should be a #14 one for #10 or #16 for #12. Use the fewest possible splices and other connections as you can. Use a relay with 40A contacts. Make the ground wire the same size as the supply wire, and ground it VERY THOROUGHLY to a place as electrically close to the battery as possible; the engine block for example, or the same chassis piece, maybe even the same screw if possible, that the small wire coming off the - batt cable goes to. Use the thickest, heaviest-duty kind of terminals where the big wires plug onto the relay; solder them - not just crimp them - and cover them with heat-shrink, self-adhesive spicing tape, or the like. Same for the ends of the fusible link. DO NOT use a plug-in fuse; that just sets you up for future intermittent connections, burned-up parts, and failures at the most awkward possible moments. There's a reason the factory used fusible links for the high-power continuous-current-flow circuits, like the cooling fan motor supply, blower motor high-speed supply, and the feeds into the cabin, instead of fuses.

 

Yeah, my Painless kit has a circuit breaker that connects inline with the 12v+ from the battery and the relay, which will be mounted on the radiator support next to the battery...